The present invention relates to a device for measuring the level of a variable signal as a function of a given parameter, such as for example time, with logarithmic conversion.
Devices effecting a logarithmic conversion by logarithmic amplifiers are already known. These devices do not always make it possible to obtain the desired accuracy and linearity. In fact, apart from the drift of the gain of the amplifiers as a function of the temperature, they present an error which depends on the level of the signal which is applied to the input of the logarithmic amplifiers. Furthermore, devices provided with a squaring and integrating chain giving the root-mean-square value of the signal to be measured are also known. The error introduced by the squaring and integrating chain also depends on the level of the signal.
It is therefore an object of the present invention to provide a measuring device more accurate and more linear than the presently available devices, particularly for frequencies reaching several tens of kilohertz, and for the case where the signal to be measured has a relatively large crest factor.
To this end, the present invention relates to a measuring device having no logarithmic amplifier and in which the level of the signal applied to the input of the squaring and integrating chain is virtually constant.